Three-dimensional (3D) printers use an additive manufacturing process consisting of laying down successive layers of a material to build a three-dimensional solid object from a digital model. Three-dimensional printers can be used for rapid prototyping, small production runs, custom fabrication, and various other uses in such applications as biotechnology, aerospace, automotive, medical, engineering, information systems, education, clothing, military, industrial, and others.
As 3D printers have developed over time, several different technologies have emerged that employ additive processing, including but not limited to extrusion of thermoplastic filaments through a heated nozzle, stereolithographic polymerization of monomeric liquids or fusable or agglomerable powders, inkjet head printing, and selective heat or laser sintering.
Stereolithography is a method for automatically building complex 3D parts by successively solidifying thin cross-sectional layers. These layers may be composed of photopolymer resin, powdered materials or the like. Some types of powder materials are converted from a fluid-like medium to a cohesive cross-section by melting and solidification. The layers are solidified on top of each other consecutively until all of the thin layers are joined together to form a completed object. This method of fabrication is extremely powerful for quickly reducing design ideas to physical form for making prototypes. A stereolithography apparatus generally includes a radiation or light source, a scanner, a container of polymerizable build material, a build surface, an elevator, and a controlling computer. Other apparatuses and methods for forming 3D objects using stereolithography are shown and described in U.S. Pat. Nos. 4,575,330; 4,752,498; 4,801,477; 5,122,441; 5,182,055; 5,609,813; 5,779,967; 5,885,511; 6,036,911; 6,492,651; 8,182,882; 8,318,055; 9,205,601; 9,211,678; and 9,216,546; as well as U.S. Patent Publication 2016/0046075, the disclosures of which are incorporated by reference in their entireties.
The common theme among all of the cited patents and publications and across all of the 3D printing applications is that the build surface upon which the 3D objects are formed is horizontal. A horizontal build surface is convenient to engineer and simplifies some printing designs and applications, but it also creates several issues that have yet to be overcome.
To facilitate an additive process that utilizes a horizontal build surface, several components, often including the build surface itself, must necessarily include a means for adjusting their vertical positions along the z-axis as the printing method progresses from layer to layer. Requiring vertical adjustability dramatically increases the complexity, precision, and care that must be undertaken in the design and use of the 3D printer. It also increases the time to form each 3D object, especially with printing applications where the building material must settle after each height adjustment in order to print the next layer.
Similarly, horizontal build surfaces which are stationary in the x- or y-axis relative to the plane of the build surface severely limit for high-throughput applications because they require a high degree of user supervision or intervention. For some uses, such as modeling, prototyping, or printing biological objects, a high-throughput device is not necessary. However, present 3D printers are generally not up to the task for large-scale production runs that require a multiplicity of 3D objects to be built with high fidelity in a short period of time. Even where a particular printer can build a set of objects at once, all of the objects must be completely formed and processed before production of a new set can begin. Present 3D printing systems that attempt to address this problem are inadequate, unfeasible on a large scale, or both.
PCT Patent Publication WO2015/056230 attempts to solve the high-throughput problem by creating a carousel system. However, the carousel system requires a plurality of trays with horizontal build surfaces, printing heads, and processing stations through which newly-formed objects must pass hundreds or thousands of times before they are completed. Furthermore, the entire carousel must shift vertically along the z-axis in order to build the next layer on each object, but only after the same layer has been formed for every object on the carousel. Thus, every object being built at any given time must be at the same (layer-by-layer) stage in the production process, and the entire set of objects must be completely printed before a new set can begin. Consequently, building 3D objects using a carousel is not a true high-throughput system that allows objects to be printed successively, one object after another.
U.S. Pat. Nos. 8,226,395; 8,282,380; and 8,287,794 utilize a conveyor belt to provide a continuous buildable surface upon which to produce 3D objects. However, because the build surface on the conveyor belt is nonetheless horizontal, it is still subject to the same pitfalls as all other horizontal build surfaces discussed above. Furthermore, by demonstrating by example only a single build method, extrusion of a thermoplastic filament, the disclosures do not adequately address how to utilize a horizontal conveyor belt system in stereolithographic applications where the vertical position of the 3D object must change in order to position the layer being built at the surface of a polymerizable liquid or fusable or agglomerable powder.
Consequently, there is a need for machines that can successfully and accurately accommodate high-throughput applications for all types of additive processing techniques to continually produce 3D objects with minimal user supervision and intervention.